Conventional cargo loading and unloading operations at a typical loading dock involves the use of a lifting mechanism, such as a fork lift, that typically removes cargo from a trailer and then transports the cargo to some sort of staging platform. Cargo including photosensitive material is normally protected from contamination by cargo containers. Despite the best manual handling practices, the incoming cargo may be exposed to ambient environmental conditions, particulate contaminants being most disadvantageous, when removed from the cargo container prior to processing. Therefore, protecting the cargo container from airborne particulate contamination which could potentially migrate to the cargo is an important factor in overall cargo management. More particularly, handling photosensitive cargo, such as film rolls, requires that the photosensitive cargo not be exposed to environmental particulate contaminants. However, because material handlers presently have to enter the dock area, remove the photosensitive cargo from the trailer and then transfer it to a conveyor accessing the clean room or environmentally controlled area, there is a substantial risk that the photosensitive cargo will become contaminated or damaged by manual handling, and thus not be suitable for processing or customer use.
Numerous prior art attempts to address some aspects of the aforementioned problem involve the use of automatic conveyor floors built into the trailer such as those described in U.S. Pat. Nos. 4,892,456, 4,948,325, 4,887,937, 4,844,684, 4,756,659, 3,905,494, 3,749,268, and 3,999,671. However, a major shortcoming of the devices described in each of these patents, such as the automated load and unload highway trailer device disclosed in Bader '659, is that there is no means for precisely positioning the trailer fixed conveyor assembly against an entrance portion of an environmentally controlled dock enclosure so as to resist introducing particulate contaminants into the controlled dock enclosure.
Another shortcoming clearly evident with the present systems is that there is no means for protecting the photosensitive cargo from contaminants during reloading onto a trailer in preparation for shipment.
Furthermore, existing systems do not provide means for automatically controlling the entire loading and unloading operation without significant operator intervention.
Accordingly, there persists a need for a system and method for transporting cargo containers, such as containers of photosensitive film material, from a cargo carrying vehicle through and between a plurality of environmentally controlled enclosures and return the cargo containers to the vehicle without exposing the cargo to particulate contamination and with minimum operator intervention.